I may be getting somewhere! MHDD didn't recognize the drive because it (MHDD) doesn't work in AHCI mode:
http://forum.hddguru.com/mhdd-doesn-...v7-t13113.html
So I set it to SATA, which I (now after more research) read is there to support "1st generation SATA":
http://www.hardforum.com/showthread.php?t=1407996
MHDD's checking the drive now, and estimates just over 2 hours more to go.
I wonder if the freezing was a problem with AHCI mode, and might not happen in SATA?
BTW, no memory errors after 26 hours of checking.